New rules have come into effect in Hong Kong designed to limit the number of pregnant women arriving from mainland China to give birth.
The number of mainlanders giving birth in Hong Kong has soared
Pregnant mainlanders must now arrange a hospital booking in advance before being allowed entry into Hong Kong.
Those more than seven months pregnant without a booking will be turned back.
Hong Kong says the influx of mainland women - who want to gain Hong Kong residency rights for their children - has strained health facilities.
Hong Kong residency rights include access to its health care and education.
A Hong Kong birth also allows women to circumvent China's one-child policy and can give them access to higher standards of medical care.
Last year, some 12,000 mainlanders arrived to give birth, leaving Hong Kong's medical facilities struggling to cope.
Now hospitals there have set up a centralised booking system and set a quota for the number of mainland mothers allowed in.
As a further disincentive to cross-border births, Chinese mothers will now have to pay double the hospital fees of their Hong Kong counterparts.
These fees must be paid in advance, at an antenatal check, in order to obtain a confirmation certificate which allows re-entry into Hong Kong.
Those over 28 weeks pregnant who do not have a certificate will be refused entry.
The Hong Kong health department plans to send medical personnel to help immigration officials implement the new rules at border checkpoints.
Hong Kong's Deputy Secretary for Health, Welfare and Food Patrick Nip said that the measures were designed to prioritise care for local women.
"The new measures can also deter dangerous behaviour by non-local pregnant women in seeking last-minute hospital admission before delivery through accident and emergency departments," he said earlier this month when the rules were first unveiled.
But the BBC correspondent in Shanghai, Quentin Sommerville, says some Chinese have criticised the measures as discriminatory.
The new measures will not apply to pregnant women of other nationalities.